<?php

/*
 * This file is part of SwiftMailer.
 * (c) 2004-2009 Chris Corbyn
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

/**
 * Provides fixed-width byte sizes for reading fixed-width character sets.
 *
 * @package    Swift
 * @subpackage Encoder
 * @author     Chris Corbyn
 * @author     Xavier De Cock <xdecock@gmail.com>
 */
class Swift_CharacterReader_GenericFixedWidthReader implements Swift_CharacterReader
{
	/**
	 * The number of bytes in a single character.
	 *
	 * @var integer
	 */
	private $_width;

	/**
	 * Creates a new GenericFixedWidthReader using $width bytes per character.
	 *
	 * @param integer $width
	 */
	public function __construct($width)
	{
		$this->_width = $width;
	}

	/**
	 * Returns the complete character map.
	 *
	 * @param string $string
	 * @param integer $startOffset
	 * @param array $currentMap
	 * @param mixed $ignoredChars
	 *
	 * @return integer
	 */
	public function getCharPositions($string, $startOffset, &$currentMap, &$ignoredChars)
	{
		$strlen = strlen($string);
		// % and / are CPU intensive, so, maybe find a better way
		$ignored = $strlen % $this->_width;
		$ignoredChars = substr($string, -$ignored);
		$currentMap = $this->_width;

		return ($strlen - $ignored) / $this->_width;
	}

	/**
	 * Returns the mapType.
	 *
	 * @return integer
	 */
	public function getMapType()
	{
		return self::MAP_TYPE_FIXED_LEN;
	}

	/**
	 * Returns an integer which specifies how many more bytes to read.
	 *
	 * A positive integer indicates the number of more bytes to fetch before invoking
	 * this method again.
	 *
	 * A value of zero means this is already a valid character.
	 * A value of -1 means this cannot possibly be a valid character.
	 *
	 * @param string $bytes
	 * @param integer $size
	 *
	 * @return integer
	 */
	public function validateByteSequence($bytes, $size)
	{
		$needed = $this->_width - $size;

		return ($needed > -1) ? $needed : -1;
	}

	/**
	 * Returns the number of bytes which should be read to start each character.
	 *
	 * @return integer
	 */
	public function getInitialByteSize()
	{
		return $this->_width;
	}
}
